In the field of display panel, with the development of high resolution display technologies, the number of pixels in unit area of a display panel is increasing, and the size of a pixel is decreasing. The linewidth of electrode wirings of pixel array in an array substrate and the black matrix in a color filter substrate is decreased accordingly, so as to maintain the opening ratio.
Light is an electromagnetic wave in nature. Due to the diffraction effect of electromagnetic wave itself, it is difficult to realize a process for narrow linewidth in traditional exposure and development processes.
In order to avoid the influence of light diffraction effect, there are provided the following existing types of mask plates to realize narrow linewidth fabrication:
Wing pattern mask design, as shown in FIG. 1, in which both sides of the non-transmissive part 01 in the mask plate are designed as sawtoothed protrusions 011 with an outer edge width b and a tooth root width c. After exposure and development, the width of resultant photoresist 012 on the substrate 04 is between b and c. This type of mask plate, due to its sawtoothed edges, can reduce diffraction of light passing through a transmissive part in the mask plate, at edges of residuary photoresist on the substrate 04, thus obtaining a better control of the width between both sides of the residuary photoresist on the substrate. Linewidth of a resultant structure such as a black matrix can be adjusted by changing the widths b and c of the mask plate. Using this type of mask plate, it is advantages to realize narrow linewidth by merely modifying the sawtooth design of the non-transmissive part in the mask plate. However, the structure obtained by this mask plate has lots of burrs on its two lateral surfaces, thus making the lateral surfaces non-smooth.
SSM (slit shot mask) design, as shown in FIG. 2, in which exposure range is adjusted by decreasing width of a non-transmissive part 02 in the mask plate, so as to obtain a photoresist with narrow linewidth. This method exactly utilizes the diffraction of light. However, it is difficult to control linewidth of the residual photoresist 021 on the substrate 04 after exposure and development. Thus, it is difficult to control linewidth of the resultant structure.
GTM mask design, as shown in FIG. 3, in which the mask plate has a non-transmissive part with different light transmittance in different non-transmissive section is used to realize narrow linewidth. For example, light transmittance of the middle region 032 in the non-transmissive part is smaller than that of the edge part 031. In the non-transmissive part shown in FIG. 3, light transmittance of corresponding sections is shown by the line 034. Although residual photoresist 033 with narrow linewidth can be obtained by this type of mask plate, it is difficult to control diffraction of light at edge of the non-transmissive part, and thereby it is difficult to control linewidth of the resultant structure.